“I was wondering if you can get FnP on a Hexrifle effect. Once hit there is no saves of any kind allowed. If you fail the charataristic test than you are removed from play. Would feel no pain stop the characteristic effect?”

For the record, the Hexrifle’s exact text reads:

A model that suffers an unsaved wound from a Hexrifle must take a characteristic test based on their Wounds value (i.e. the one on their profile, not their current Wounds), If they fail the test, they are removed from play, with no saves of any kind. Vehicles cannot be affected by Hexrifles.